1. Field of the invention
The present invention relates to a fuel injection control apparatus for an internal combustion engine, and more particularly to a control apparatus for a fuel injection system capable of exhibiting excellent performance, especially when the engine is accelerated or decelerated.
2. Description of the related art
When an automobile is accelerated or decelerated, the degree of acceleration or deceleration is determined depending on the amount of actuation of the accelerator pedal by the driver. If a driver wants to drive the automobile faster, he will further depress amount the accelerator pedal, and if he wants to slow down, he will release the pedal to some extent.
However, the amount of actuation of an accelerator pedal is caused by the indefinite or fuzzy will of a driver. He usually has his will not so definitely set as to want to drive 5 km/h or 20 km/h faster than the present speed, but so indefinitely set that he wants to drive "somewhat" or "much" faster.
On the other hand, when an automobile is accelerated, the engine thereof is supplied with an air-fuel mixture, which is enriched by a predetermined quantity of fuel. This is known as a so-called acceleration enrichment. Further, in an engine which is subject to such an acceleration enrichment, it is also known that fuel is cut off, when the automobile is decelerated. The fuel supply control as mentioned above is described, for example, in the first column of U.S. Pat. No. 4,589,389 issued to Kosuge et al in 1986 and assigned to the same assignee.
By the way, in conventional fuel supply control, the aforesaid acceleration enrichment has been always automatically carried out by increasing a certain amount of fuel, when an opening of a throttle valve exceeds a predetermined value. The amount of fuel to be increased is determined definitely depending on the load of the engine (cf., for example, Japanese Patent laid-open publication JP-A-58/15725 (1983)). Similarly, the cut-off of fuel has been done automatically when deceleration is required.
Therefore, a conventional control apparatus has not always been suited for reflecting the driver's fuzzy or indefinite will as mentioned above on the fuel supply control. The present invention is intended to cope with the fuzziness in the driver's will by applying a so-called fuzzy reasoning or fuzzy technique to a fuel injection control system for an internal combustion engine.
Incidentally, the application of the fuzzy technique to a control device for automobiles has been known, for example, by the article "Application of A Self-Tuning Fuzzy Logic System to Automatic Speed Control Device" by Takahashi et al, Proc. of 26th SICE Annual Conference II (1987), pages 1241 to 1244.
Briefly, this article discloses an automatic speed control device, in which the fuzzy technique is employed for the purpose of evaluating the difference between a target speed set and an actual speed detected and, on the basis of thus evaluated speed difference, the opening of the throttle valve is controlled such that the actual speed follows the target speed set. In this article, however, there is no disclosure of the application of the fuzzy technique to a fuel injection control system.